The invention relates to a photovoltaic module in the form of a laminate, which exhibits a solar cell system along with encapsulation materials provided for it. A procedure for its manufacture is also disclosed according to the invention.
Photovoltaic modules are used for generating electrical energy from sunlight. The energy is generated via the solar cell system, which preferably consists of silicon cells. However, these can only carry a slight mechanical load, so that they must be enveloped on either side by encapsulation materials. Encapsulation materials can be one or more layers of glass and/or plastic films and/or plastic film composites.
Plastic film composites essentially comprised of polyvinyl fluoride (PVF) and polyethylene terephthalate (PET) are produced by the applicant under the designation ICOSOLAR, and used to manufacture photovoltaic modules in a vacuum-lamination procedure disclosed in WO-A1-94/29106. In these modules, the solar cell system is protected not only against mechanical damage, but also against exposure to the elements, in particular water vapor. An intermediate layer made out of aluminum is provided in the ICOSOLAR film composite as a barrier layer against water vapor. However, the disadvantage to this layer is that it is electrically conductive in conjunction with the solar cell system, so that undesired outside currents in the photovoltaic module come about.
Therefore, the object of the invention is to provide a photovoltaic module of the kind mentioned at the outset which does not exhibit this shortcoming, but is largely impermeable to water vapor.
This object is achieved according to the invention by means of a proposed photovoltaic module, characterized by the fact that at least one encapsulation material layer consists of a sealing and barrier layer, and that the barrier layer is made out of a plastic film or a plastic film composite, which is provided on the side facing the solar cell system with an inorganic oxide layer separated out of the vapor phase.
Another advantage to the photovoltaic module according to the invention is that the inorganic oxide layer consists of the elements aluminum or silicon, and is present in a thickness of 30 to 200 nm. The organic oxide layer also exhibits the advantage that it is permeable to light beams in the visible light wave range and near UV wavelength range, while it absorbs them at shorter wavelengths in the UV wavelength range.
The photovoltaic module according to the invention also exhibits the advantage that the sealing layer is arranged between the solar cell system and the barrier layer, and preferably consists of ethylene vinyl acetate (EVA) or ionomers.
According to the invention, the plastic film on which the inorganic oxide layer is deposited additionally consists of polyethylene terephthalate (PET) or ethylene tetrafluoroethylene copolymer (ETFE).
Other advantages of the photovoltaic module according to the invention are that the inorganic oxide layer faces the solar cell system, and contacts the adjacent sealing layer directly or via a primer coat.
In addition, the inorganic oxide layer is enveloped by plastic films or composites on both sides according to the invention, wherein at least one plastic film or one plastic film composite acts as the barrier layer. In this case, the inorganic oxide layer advantageously contacts the plastic films or composites via an adhesive layer and/or a hybrid layer comprised of organic/inorganic networks.
According to the invention, the inorganic oxide layer consists of SiOx, wherein the atomic ratio of silicon to oxygen x lies within a range of 1.3-1.7.
The invention also relates to a procedure for manufacturing a photovoltaic module, wherein it is beneficial for:
a) a plastic film or plastic film composite to be provided with an inorganic oxide layer separated out of the vapor phase,
b) a module stack comprised of the solar cell system and encapsulation materials to be layered in such a way that the sealing layers envelop the solar cell system on both sides,
c) this module stack to be incorporated into a loading station of a process arrangement in which it is kept at a temperature below the distortion temperature of the sealing layers,
d) the module stack to be transported to a vacuum laminator in this arrangement, which is evacuated, and in which the module stack is heated to the distortion temperature of the sealing layers, and
e) the composite formed out of the module stack, after ventilating the vacuum laminator without recooling, to be transported to a hardening furnace, in which the sealing layers are hardened, so that a laminate is formed as a photovoltaic module, which can be removed from the continuous process after recooling.